"The half-mens [Pachypodium namaquanum], growing in the same [Namib] desert, has reduced its leaves to one small bunch sprouting from the top of a pillar-like trunk bristling all over with ranks of long spines that must deter many a thirsty animal from gnawing it in search of liquid." (Attenborough 1995:272)Learn more about this functional adaptation.

Attenborough, D. 1995. The Private Life of Plants: A Natural History of Plant Behavior. London: BBC Books. 320 p.

Leaves are not divided into smaller leaflets (simple). Leaves may appear one at a time (singly) with each occurrence on alternating sides of the stem (alternate),[3] but usually[citation needed] occur in pairs or in whorls. When paired, they occur on opposite sides of the stem (opposite), with each pair occurring at an angle rotated 90° to the pair below it (decussate).

There is no stipule (a small leaf-like structure at the base of the leaf stem), or stipules are small and sometimes fingerlike.[3]

In continental southern Africa (Angola, Botswana, Mozambique, South Africa, Swaziland, and Zimbabwe) and Madagascar, except for the humid evergreen forest of the eastern side of Madagascar, and never above 2000 m for the entire island: Pachypodium and Fockea

^Angiosperm Phylogeny Group (2009). "An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG III". Botanical Journal of the Linnean Society161 (2): 105–121. doi:10.1111/j.1095-8339.2009.00996.x.